1. Field of the Invention
The present invention relates to a device for measuring switching force in railway points, this having a sensor and a measuring bolt that is in the form of a deformation body that is connected to the sensor and which can be inserted into a joint in the points drive.
2. Prior Art of the Invention
A device of the type described above, designated "BKM," has already been brought to market by FEHA as a switching force meter. The known switching force meter consists of a slotted steel body as a deformation body, and this accommodates a dial as an indicating instrument and an attachment device. The known switching force meter is used to measure the forces that occur between the points drive and the points, regardless of whether these forces act from the point drive onto the switch blades or as residual forces in spring point blades or as impact force against the retaining force or against the impact resistance of the points drive. To this end, the measurement bolt is inserted in a cardan joint or in a biaxial joint in place of a point connector bolt, and when this is done transverse bending beams are formed by the slots in the steel body. In the known device there are bead-like thickened portions on the outside and these serve in each instance as the point of application for the forces. A dial is provided as a measuring or indicating instrument on the bending beam that is extended upwards. A retaining device is provided to ensure the correct orientation of the measurement bolt in the particular joint, and this fits into the slot of the measuring bolt and is intended to prevent any axial displacement of the measurement bolt. Taken all in all, this results in a mechanical measuring device which, for a given level of precision, must display a high degree of mechanical sensitivity and for this reason must be particularly well protected during transportation and installation. The danger of damage to a mechanical switching force meter is naturally relatively high, and because of the retaining device that is selected, and which fits into the slot, some distortion of the forces that act on the bending beams can occur. Apart from mechanical measuring devices of this kind, a number of electro-mechanical force meters for bolts in joints are already known. For example, DE-A1 35 15 126 describes an electro-mechanical force meter in which at one end a rigid measuring rod and at the other bolt end a sensor are inserted into a cavity in a tubular bolt. Arrangements of this kind are vulnerable to vibration and entail the risk that all adjustments and calibration can be lost during installation and removal of the tubular bolt, so that replicable measurements during the demanding conditions of railway operation are not possible unless additional steps are taken. The same thing applies for the force meter that is described in DE-A1 34 34 843, in which, in the same way, a disk-shaped carrier is fixed in the interior of a cavity in a bolt, this carrier having strip-type strain gauges. During the installation and removal of a tube-shaped bolt of this kind there is a danger that the leads and conductors for the strain guages will be over-stressed. Simple insertion and removal of a bolt of this kind without the use of costly tools is not possible without additional measures being taken.